package approval

import (
	"encoding/json"
	"fmt"
	"strings"

	"git.novox.be/novox/mesh-contracts/operator-and-conversation/go/clients/operatorchannelclient"
	seat "git.novox.be/novox/mesh-contracts/operator-and-conversation/go/seats/operatorchannel"
)

// Run is a call through the gate (§20): an unmarked call runs; a marked one runs only on the operator's approval of that
// one call, judged on the router's record and claimed once (§14, §15), and is otherwise answered as an error saying why
// (§12, §17, §19). run is called at most once.
func (g *Gate) Run(c Call, run func() (any, error)) (any, error) {
	m, err := g.marksOf(c)
	if err != nil {
		return nil, err
	}
	if missing := g.unservedOf(c.Module); len(missing) > 0 {
		return nil, fmt.Errorf("Not run: %s's marks name %s, which its bundle on %s does not register, so none of its tools is "+
			"served here (design 46 7-approval-mark §4)", c.Module, strings.Join(missing, ", "), g.d.Node)
	}
	marked, _ := m.Marked(c.Seat, c.Name)
	since := g.markedSince(c, marked, m.Revision)
	if !marked {
		return run()
	}
	if c.Own {
		return nil, g.refused(c, "", "it is one of the tool runner's own tools, which no ask covers")
	}
	if m.Unread != "" {
		return nil, g.refused(c, "", m.Unread)
	}
	if b, ok := g.d.State.(Binding); g.d.State == nil || ok && !b.Bound() {
		return nil, g.refused(c, "", "the tool runner's membership binds no state "+StateName+" to keep its asks in")
	}
	if why := refusedUnasked(c.Args); why != "" {
		return nil, g.refused(c, "", why)
	}
	if why := g.held(); why != "" {
		return nil, g.refused(c, "", why)
	}
	act, err := ActOf(c, g.d.Node)
	if err != nil {
		return nil, g.refused(c, "", err.Error())
	}
	digest, err := operatorchannelclient.ActDigest(act)
	if err != nil {
		return nil, g.refused(c, "", err.Error())
	}
	named, err := g.d.State.Get(g.actKey(digest))
	if err != nil {
		g.stateFailed(err)
		return nil, g.refused(c, digest, "its state "+StateName+" cannot be read: "+err.Error())
	}
	g.stateRead()
	if named == nil {
		return nil, g.raise(c, act, digest, since)
	}
	var id string
	if err := json.Unmarshal(named.Value, &id); err != nil || id == "" {
		return nil, g.refused(c, digest, fmt.Sprintf("its act's key in %s names no ask", StateName))
	}
	return g.judge(c, act, digest, id, since, run)
}

// Binding is a Store that says whether the runner's membership binds the state now (§13).
type Binding interface{ Bound() bool }

// marksOf is the module's marks as the catalog half has them now; before its first view, the call waits for it within
// RecordWithin and is then judged, refused naming mesh_first_views when it is still unread (§19).
func (g *Gate) marksOf(c Call) (Marks, error) {
	if g.d.Catalog == nil {
		return Marks{}, g.refused(c, "", "the tool runner reads no catalog half, so its marks are not read")
	}
	if err := g.d.Catalog.Ready(); err != nil {
		if g.d.Wait != nil {
			err = g.d.Wait(RecordWithin)
		}
		if err != nil {
			return Marks{}, fmt.Errorf("Not run: the marks of %s are not read yet (%v); mesh_first_views says what the tool runner "+
				"waits for", c.Module, err)
		}
	}
	m := Derive(g.d.Catalog, c.Module, c.Fingerprint)
	g.checkServed(m)
	return m, nil
}

func (g *Gate) unservedOf(module string) []string {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.unserved[module]
}

// markedSince is the revision a call was marked at when the same caller last called it unmarked (§12), empty otherwise.
func (g *Gate) markedSince(c Call, marked bool, revision string) string {
	key := c.Caller + " " + c.Address
	g.mu.Lock()
	defer g.mu.Unlock()
	if g.unmarkedAt == nil {
		g.unmarkedAt = map[string]bool{}
	}
	was := g.unmarkedAt[key]
	if marked {
		delete(g.unmarkedAt, key)
		if was {
			return revision
		}
		return ""
	}
	g.unmarkedAt[key] = true
	return ""
}

// judge is the same call made again, judged on the router's own record of its act's newest ask (§14 to §17).
func (g *Gate) judge(c Call, act operatorchannelclient.Act, digest, id, since string, run func() (any, error)) (any, error) {
	rec, err := g.record(c.Module, id)
	if err != nil {
		return nil, g.refused(c, digest, "the router's record of its ask "+id+" cannot be read: "+err.Error())
	}
	if rec == nil {
		return nil, g.firstAnswer(c, id, digest, since) // §17: not yet taken by the router
	}
	again := func(why string) (any, error) {
		err := g.raise(c, act, digest, since)
		return nil, fmt.Errorf("The ask %s %s; asked again. %w", id, why, err)
	}
	switch rec.State {
	case "open", "held-back":
		return nil, fmt.Errorf("Not run: still waiting for the operator's answer to ask %s (fingerprint %s); it expires at %s",
			id, Fingerprint(digest), rec.Expires)
	case "refused":
		return nil, g.refused(c, digest, "the router refused its ask "+id+": "+orNone(rec.Answer))
	case "chosen":
	default: // expired, cancelled, replaced: each asks again (§15, §17)
		return again("ended " + rec.State)
	}
	w := rec.Warrant
	if w == nil {
		return nil, g.refused(c, digest, "the router's record of its ask "+id+" is chosen and carries no warrant")
	}
	at, _ := operatorchannelclient.Time(w.At)
	if w.Option == OptionDecline {
		if until := at.Add(DeclinedFor); g.d.Now().Before(until) {
			return nil, fmt.Errorf("Not run: the operator declined ask %s; the same call is not asked again until %s",
				id, operatorchannelclient.FormatTime(until))
		}
		return again("was declined more than 10 minutes ago")
	}
	if g.d.Now().After(at.Add(RunWithin)) {
		return again("was approved too long ago (more than 30 minutes)")
	}
	var answer any
	var ran error
	h, err := g.client(c.Module).Take(*w, func(o seat.Option, _ seat.Warrant) error {
		if err := operatorchannelclient.Performs(o, act); err != nil {
			ran = err
			return err
		}
		answer, ran = run()
		return nil
	})
	switch {
	case h == operatorchannelclient.Done:
		return again("was already run")
	case h == operatorchannelclient.Refused:
		return nil, g.refused(c, digest, "its warrant does not hold: "+errText(err))
	case h == "" && err != nil:
		g.stateFailed(err)
		return nil, g.refused(c, digest, "its state "+StateName+" cannot be written: "+err.Error())
	case err != nil: // the act about to run is not the one the option bound: nothing runs, the warrant stays used
		return nil, g.refused(c, digest, err.Error())
	}
	return g.ran(c, id, rec, answer, ran)
}

func errText(err error) string {
	if err == nil {
		return "no reason given"
	}
	return err.Error()
}